O'Driscoll had not played for Leinster since the final round of Heineken Cup Pool matches and missed out on the Amlin CC quarter-final win over London Wasps because of a suspension picked up during the RBS 6 Nations.
"I'd put that up there with our most physical games of the season, the ones against Clermont," admitted Leinster head coach Joe Schmidt after seeing his side hit back to win.
The visitors lost wing Dave Kearney in the second half after he was knocked unconscious in an incident involving Munster lock Paul O'Connell. Kearney was taken off the field on a stretcher and is set to miss a few weeks of action.
"Dave was unconscious for a while but he's fine. He was concerned about whether or not he'd caught the ball," said Schmidt. "He'll miss a few weeks now, which is a frustration to him because he had reached a rhythm."